Electron discharge tube



Sept. 7, 1948. P. w. sTuTsMAN ELECTRON DISCHARGE TUBE Filed May 5, 1944 l A y@ llllulllllllll/l Patented Sept. 7, v1948 lELECTR'ON DISCHARGE TUBE Paul W. Stutsman, Needham, Mass., assignor, by mesne assignments, to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application May 5, 1944, Serial N0. 534,292

6 Claims. (Cl. 25027.5)

This invention relates to electron discharge tubes.

One object of the invention is to provide an electron discharge tube with an auxiliary electrode that will produce a greater flow of electrons from the cathode to the plate and a relatively high ratio of increase in plate current to current drawn by said auxiliary electrode, so that current drawn by said auxiliary electrode is unobjectionable. l0

This and such other objects of the present invention as may hereinafter appear will be readily understood from the following description taken in connection with the accompanying drawing of two illustrative embodiments oi the invention herein presented for illustrativepurposes.

In the drawing: j

Fig. l is a longitudinal section, on an enlarged scale, of an electron discharge tube incorporat- 20 Fig. 5 shows diagrammatically the tube Villustrated in Figs. 1 and 2 and an illustrative circuit for the device.

I have discovered that if a positively charged thinA wire auxiliary electrode, of which the crosssectional diameter is below aV certain critical value, described below, be inserted in an electron discharge tube adjacent the cathode, and be charged to a suitablerpositive potential, said thin wire auxiliary electrode will produce a suiiiciently high ratio of increase in plate current to current drawn by said thin wire auxiliary electrode to reduce the current drawn by said thin wireauxiliary electrode to below an objectionable level.

v For convenience the invention will be described and illustrated with one or more of my novel auxiliary electrodes added to a triode, but it is to be understood that such novel electrodes can be Vadded withr like advantage in other'electron discharge tubes having two or more electrodes.

Referring more particularly to Fig. 1, the illus- A trative embodiment of the invention therein disclosed comprises a vacuum tube consisting of an hermetically sealed envelope 2 of glass or other suitable material and containing an electrode assembly comprising an electron-emissive cathode 4, an anode or plate 9, a control grid 8 and my novel thin wire auxiliary electrode I0 of tungsten or any other suitable metal or alloy. In the present embodiment of the invention the cathode illustratively consists of a filament of the thermionic type but the invention contemplates the use of a cathode of any suitable type. cross-section or structure. Any suitable grid may be used, circular, or of any other suitable type. In this illustrative embodiment of the invention the grid 8 is elliptical in cross-section and said cathode filament 4 extends through the center of the ellipse perpendicularly to the plane-of the'drawing (see Fig. 2). My novel thin wire auxiliary electrode I0 extends substantially parallel to said cathode and intersects the major axis of the ellipse at a point between said cathode and said grid 8. However, instead of being straight, my novel thin wire auxiliary electrode may be of any other suitable shape. Said cathode filament 4 and said thin wire auxiliary electrode I0 pass through the upper and lower spacer members 3 and 5 of mica or other suitablematerial, their upper ends being secured to resilient wires 'I and 9 respectively, said wire 1 being connected to the upper end of conductor I l and said wire 9 to the upper end of a dummy post I3. Said .conductor II and post I3 extend through apertures'in said two spacer members 3 and 5, their lower ends being sealed through a. press I5 formed upon the top of the reentrant stem I1 of said envelope 2, said envelope having its lower edge hermetically sealedto the flare I2 of said stem I1. The lower end of conductor II is connected to alead-in wire I1. The anode or plate Ii is supported by two side bars I6 and I8 having their lower ends sealed in said press I5, the bar I8 serving as a conductor for said plate 6 and having its lower end joined to a lead-in conductor I9 sealed through said press.

The grid is carried by posts 20 and 2I.. The lower ends oi' said cathode lament 4 and the thin wire auxiliary electrode II) are connected by conductors 22 -and 23 tolead-in wires 24 and 25 respectively, sealed through said press I5, and the grid post 20 is connected by a wire 26- and conductor 21 to a lead-ln wire 28` also sealed through said press I5.

The cathode 4 may be heated in any suitable manner as by a battery 29 (see Fig. 5), for exs; ample, and the cathode-anode circuit comprises a source of D. C., such as a battery 30, the positive pole of which is connected to the lead-in wire i9 of said plate by conductor 3| containing a resistance 32, the negative of said battery 30 being connected to the cathode 4 by a con'- ductor 33. The grid 8 is connected to the cathode l byjafconductor 3S through condenser 31, the signall input' and' conductors 39, 40 and 33. An output circuit is diagrammatically indicated at 4l and is connected across the resistanceV 1 32. A conventional grid leak comprising asuitable resistance 43 will preferably beprovi'd'ed'as shown in Fig. 5.

As above Stated' I have ds'everedthatthe* cross-sectional diameter of -Lmynovel-fthin wire auxiliary electrode l0 should be below a certain critical value which I have found tor-be about '.Thefsmallerthe cross-sectional diameter of said 1 thinfwire auxiliary electrode below the aforesaid critical value, theqhigher willbe the ratio of plate current to .current drawn by, said thin wire auxiliaryelectrode, lcut;there isa limitto the thinness ottheiwire. auxiliary electrode beyond which the sa,id .thin wire auxiliary electrode becomes too frailgto be usable. I haveffound' that in Jpractice it ,ris :not -advisab1e to -use ia thin .wire-auxiliary electrode, the cross-sectional diameter of which is liess thangabout .0.0005 inch, except possibly in cases 4.where .the wire possesses unusual tensile strength.

1-have also discovered that thefavorableratio ofincrease in plate current to auxiliary electrode current eattributabletothe action of my Vnovel thin Wireauxiliaryelectrode is also dependent on itsgzspacinggfromthe cathodeand below a certain .critical .1 spacing .varies with :the -spaeiris .of Said thin wireauxiliar-y @electrode from the cathode. f Ihe nearerihe thin Wirefauxiliary electrode is to the cat1iode, the higher will be the .ratio vof increase irrplate current t0 currentdrawnbv-said thin -wireiauzliary electrode In this vConnection certain factorsare to be considered. For :example,. in use there'ls always :more l,or-.less vibration of the .thin wire auxiliary electrode and of the cathode flament, a nd the vspacing vof said thin nare-auxiliary electrode relatively to .the cathode must .notihe so. close asterisk .shortfeirsuitine from'this c ause. If said thin wire auxiliaryelectrode andthe f llamentare under suitable tension, thespacing `fromeach other may be less than if this-is notthegcase, but the tensile strength of a wire .orlament varies yand such variation rmay -thereioreyhave va 'bearing on thespacing .of the .thin =wire auxiliary electrode from the lament. Intshorter tube structuresthe-fllament, and-therefore .theithin wire auxiliaryelectro de, areshorter, @11d .therefore ythe vamplitude of vibration tends .to tbe less, A another lfactor .to be considered in determining the spacing.

For the above reasons I have foundthat -it is .generally inadvisable toplace the thin --wire aux iliaryanyfnearer tothe cathode than about. 0 .007

finch. -Qn the other. hand, 1 have-discoveredthat 4 the thin wire auxiliary electrode should be spaced from said cathode a distance below a critical value which is about 0.015 inch; otherwise the increment to the plate current becomes of the order of the wire current with respect to changes in the positive potential on the thin wire auxiliary electrode. The illustrative embodiment of the invention shown in Figs. Sand 4 may and preferably will be the same as the above-described illustrative embodiment of the invention shown at Figs. 1

and 2, with the exception that a second thin wire illustrated in Zsaid Figs. 3 and 4 have therefore beendesignated byithe same reference numerals as the corresponding parts of the illustrative embodiment of the invention shown in Figs. 1 and 2.

'Referring to said Fig. 3, the second thin wire auxiliary electrode 45 of my invention is connected at its upper end by a resilient wire l2 to the upper end of the .conductor I3 and at its lower ende-.to conductor 23 to which the other thin wire auxiliary electrodel isfconnected as previouslydescribed, so that the lead-in wire ,25 Yconnects both thin wire auxiliary electrodes l0 and 05toaconductor te (see Fig. 5) connected to the vcathodeanode circuit containing the aforesaid battery '30. Both of saidthin wire auxiliaryelectrodes liland i5 Athus lreceive apositive potential.

The addition of this second fine wire auxiliary electrode 45 in accordance withmy inventionadds a material Aincrement Yto theincrement addedto the platecurrent by the thin Wire auxiliary velectrode I vI have found that with the two thin Wire-.auxiliary electrodes L0 and .45, the increment added to the, plate current issubstantiallyzdouble the increment 'added by the single thin wireauxiliary electrode l0. It will be apparentzthat additional' thin wire auxiliaryelectrodes inaccordance with. my .invention may beaddedwithout departing from thescope ofthe present invention.

It will be noted lthat in both the illustrative embodiments of the inventionabove described, thesupports for the thin.wire auxiliaryelectrodes are so situated that no undesired current `from the cathode can flow .to them. Where there is danger of a discharge from the cathode-emitting surface flowing to the conductive supports of .the thin wire auxiliaryelectrodes, means may beprovided to .prevent it.by.making said supportsof non-conductive material or coating them .with a non-conductive material, ,for example.

Wherever the expression a plurality is used in the specication and appended claims,: it .is to be .understood as meaning `.two .or more.

I am aware that the present inventioncan be embodied in other specific forms lwithoutfdeparting `from the -spirit or the essentialattribu-tes thereof, and vI therefore desire the1present'1description to be considered in, all ,respects as illustrativeand not restrictive, reference being-had to the appended claims ratherrthan tothe-aforesaid dscription ,to indicate-the scopeof 'theinvention.

What is claimed is: Y A -1. An electron discharge tube comprising r-an hermeticallyp-sealedr envelope containing -anfelectrode lassembly ,comprising an electron-emissive cathodaananode, and aV thin wire auxiliary electrode adjacent -said cathode, the cross-sectional diameter of said auxiliary Velectrode being -less than a critical valueof about 0.0015 inch, and the vspacing of said auxiliary electrode from'said cathode being .less than `a critical value-of about .oms-inch.

2. An electron discharge tube comprising an hermetically sealed envelope containing an electrode assembly comprising an electron-emissive cathode, an anode, and a thin wire auxiliary electrode extending substantially parallel to said Icathode adjacent the latter, the cross-sectional diameter of said auxiliary electrode being less than a critical value of about 0.0015 inch, and the spacing of said auxiliary electrode from said cathode being less than a critical value of about 0.015 inch.

3. An electron discharge tube comprising an hermetically sealed envelope containing an electrode assembly comprising an electron-emissive cathode, an anode, a grid, and a thin wire auxiliary electrode adjacent said cathode, the diameter of said auxiliary electrode being less than a critical value of about 0.0015 inch, and the spacing of said auxiliary electrode from said cathode being less than a critical value of about 0.015 inch.

4. An electron discharge tube comprising an hermetically sealed envelope containing an electrode assembly comprising an electron-emissive cathode, an anode, and a plurality of thin Wire auxiliary electrodes adjacent said cathode, each of said auxiliary electrodes having a cross-sectional diameter that is less than a critical value of about 0.0015 inch, and the spacing of Said auxiliary electrode from said cathode being less than a critical value of about 0.015 inch.

5. An electron discharge tube comprising an hermeticall'y sealed envelope containing an elec`- trode assembly comprising an electron-emissive cathode iilament, an anode, and a thin wire auxiliary electrode adjacent and substantially parallel to said cathode, the cross-sectional diameter of said auxiliary electrode being less than a critical value of about 0.0015 inch, and the spacing of said auxiliary electrode from said cathode being less than a critical value of about 0.015 inch.

6. An electron discharge tube comprising an hermetically sealed envelope containing an electrode assembly comprising an electron-emissive cathode, an anode. and a thin wire auxiliary electrode adjacent said cathode, the cross-sectional diameter of said auxiliary electrode being less than a critical value of about 0.0015 of an inch.

PAUL W. STUTSMAN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,134,407 Jonker Oct. 25, 1938 2,141,303 Jonker Dec. 27, 1938 2,325,664 Cohn Aug. 3, 1943 FOREIGN PATENTS Number Country Date 229,019 Great Britain Feb. 19, 1925 

